Magnetic material, method of making the same, and articles made therefrom



metowosmows, I

comma e ara a" 8 fatented 5,193; I

magnetic cores may .5 acid, together with sifted, after 1 CROSS REFERENCE s e 'T'su'rf or'r'lc's "owns 0. memoirs, or chrome, rumors, Assumes. To

conrm, 1nconrom'rnn,or NEW Yoax, N. 1.,

or mme rim sure, am anrrcnss mu rmmnrnorr 4 meme miraam, usrnon Io Drawing. Application filed December This invention relates to a magnetic material, amethod of making the same, and articles made therefrom, and more particularly to a material for making magnetic core 5 parts of'the compressed dust type for use in tele honic communicating systems, to a -met 0d of making such material, and to magnetic core parts madefrom such ma terial.

An object of the invention is to produce a magnetic material which will withstand high forming pressures and high treating temperatures, is non-corrosive, non-oxidizing, has a low aflinity for water, and from which factory mechanical and electrical properties and having very low. water absorbing characteristics.

a v In one embodiment of .the invention, the g 20 magnetic material consists of a ma etic al- 10y in finely divided form, the par 1c es of which are insulatgd from each other by an. insulating composition which includes a wafer-solulileso fgiiifilfigid, such as tartaric P dditi l i 'fgdfifl' alloy employed, and of the manner of preparsuch as sodiumsilicate, talc, and kaolin. The imam-amateurs is intimates mixed with the particles of the alloy, and the resulting material is heated to dr ness and which the materia 1' ""'p ressed into cores suitable vfor use in telephonic cominunicatin systems.

Other 0 jects and advantages of the in ventionwill become apparent from the fol,-

lowing description.

In practlcmg the present invention, the

' magnetic material. is preferably prepared vfrom a brittle alloy containing nickel and iron, with or without the addition of other 40 constituents, and commonly known as er 'Tbe alloy may be prepared 1n tEe f manner described in Patent No. 1,669,649 issued May 15?, 1928 to C. P. Beath and H. M. E; Helnicke, wherein approximately 81 parts of nickel'and 19 parts of iron are melted together in an oxidizing atmosphere,

the resulting alloy being poured into a mold. 'The'alloy thus prepared is rolled while hot into relatively thin slabs which are quenched rapidly to produce a fine crystalline strucbe produced of satis-.

A GOBIORATION OF NEW YORK 31, 1980. $er1a1 No. 505,958.-

Examiner ture which is desirable since the disintegration of the material takes place at the crystal boundaries the size oi I the crystals the finerthe dust which can be produced therefrom. The slabs are then reduced to a finely divided form in.

any suitable manner and the finely divided alloy is subsequently. reduced to a dust by pulverizing it in an attrition or ball mill. The dust from the attrition or ball mill is then sifted and the portion passing through a 120-mesh screen is placed m a closed con tainer and annealed at a temperature of approximately 885 removed from the container in the form of a cake, which is again reduced to a powder by crushingit in a rotary crusher'and subsequently grinding it in an attrition mill, the

ing the metal or alloy. The term. magnetic metal, as used herein, is therefore intended to mclude any magnetic metal "or alloy of metals suitable for use in connection with the present invention, regardless of its composition or method of preparation.

As an example of an insulating composition suitable. for the purposes 0 e pres ent lnvention, the following formula s given:

1 4 Pounds Tartaric acid -l 30 Sodium silicate 1. 05 Powdered talc Kaolin l l r r; a .75 Water 12.00

The ratio of acid tosodium silicate as given in the above formula is 123V, but may range from 1: 3 to 1: 8 or upwar s, the

efiectlveness of the insulation decreasing C. The annealed dust is round dust is again sifted through a 120- and consequently the smaller somewhat as the ratio of aci to sodium silicate decreases from that given in the above formula. The ratio of the solid materials (talc and kaolin; to the water-soluble materials (acid and sodium silicate) ma be va ried widely, a's may also the ratio of water er ingredients, the water being used merely to dissolve the water-soluble materials and to give the desired consistency to she mixture of insulating composition and ust. l V

The lraolin specified in the above formula is a binfi irand has the function of preventing cracks in the finished core parts, in addition to being a rather effective msulat-' ing materiaL. In certain cases it may be omi tjgd de ndin upon the characteris 1 e "usual toroidal windin to remove such water-absorbent substances. The tartaric acid used is a very weak oxidizing agent, and since it volatilizes at a relatively low temperature very little oxidation of-the metal takes place during. the annealing operation. Such oxidation may be objectionable-in some cases since it appears to afl'ect unfavorably the magnetic qualities of the finished cores.

Que or more core-parts thus formed are then used to constitute a core to which the is applied to form a loadin coil, the num r o core'partsused depen mg is 'to be associated. i

In place of the tartaric acid specified'in upon the electrical characteristics of the circuitwith which the loading coil 0 to which the finished cores areto. be put. so For most urposes, the amounts specified in the above ormula would be mixed with about 100 pounds of dust. The entire mass is then evaporated to a condition of complete dry; ness in orer n m n- .rfiax1mu'm"iiiuthe above formula, any other suitabl aterl soluble organic acid may 5 usedfaltlfofi'gli' lation resistance, and is stirred. constantl l to an annealing to prevent cakin and to insure a thorou coating of the in ividual dust particles. 0 obtain a complete drying of the magnetic material its temperature may be raised-to 120 0., and even much higher temperatures maybe used without injury to the material. The material after being thoroughly dried has a ve low aflinity for water, so that no specia rotection need be provided against the a rption of water by the material.

The insulated dust is then sifted through a 16-mesh screen, placed in a mold and compressed into core parts under a pressure of approximately 200,000 pounds per. square inc The core Parts are then transferred urnace where they are annealed to relieve the internal stresses set up by the pressingoperation and thereby to roduce a core having low hysteresis loss. he annealing temperature used is prefe-rabl about 565 0., but a tem rature as big as 620 C. may be used without destro ing the efiectiveness of the insulation. ere

, a temperature of 565 is used, the core parts are preferably raised to that temperature in about eleven minutes and maintained .at such.

temperature for about three minutes Ifhigher annealing temperatures are used the time should of course be proportionately shortened, and vice versa.

The drying and annealing temperatures ap arently drive of! substantially all of the 'vo atile constituents of the material, including the organic acid, in the form of gases,

with the result that the annealed core parts contain only the end-products of the'heating process, and contain no water-absorbent substances. This makes itunnecessar'y to .wash and dry the coreparts after annealacid.

vvided particles of a magnetic metal, and an ated with said 5 ceramic inding material.

oxalic, and malonic aci invent-ion is not limited to the embodiments above described, but may be varied widely within the scope of the following claims: p

What is claimed is: I

1. A magnetic material suitable for pro-- ducing magneticcores, comprisin a finely divided magnetic metal, and an insulating composition mixed therewith and including .a water-soluble organic acid.

I 2. A magnetic material suitable for producing magnetic cores, comprising finely divided particles of a magnetic metal, and an insulatmg composition intimately associated with said particles and including tartaric 3. A magnetic material suitable for producing magnetic cores, comprising finely diinsulating composition intimately associ-v acid.

4. A ma'gnetic material suitable for producing magnetic cores, comprising finely divided particles of a ma etic metah'and'an insulatm composition intimately associated with sai particles and including citric acid. j 5. A composition of matter comprising finely" divided ma etic metal, a water-soluble or nic aci sodium silicate, and a 6. A composition of matter "omprising the following ingredients in about the fol lowing proportions: finely, divided magnetic metal, parts; (tartaric acid, 0.30 parts; sodium silicate,. 1 .05 parts; powdered talc, 0.75 parts;.and kaolin,0.75 parts.

-7.' A magnetic material comprisingfin 'ely divided magnetic metal, and an insulating composition forming a coating on the par-' 11c particles andincluding lactic ticles of metal and including the end-products obtained by heating a mixture of a water-soluble organic acid, sodium silicate, and talc,

- binding material, and water,

- water,

to a temperature above 400 (J.

8. A method of producing a magnetic material which comprises mixing together a finely divided magnetic metal, a water-soluble organic acid, sodium silicate, a ceramic and evaporating the resulting;mixture to complete dryness. 1 i

9. A method of producing a magnetic material which comprises mixing a finely divided magnetic metal with an insulating composition including a water-soluble or amc acid, sodium silicate, a ceramic materia and and heatingthe resulting mixture to drive off substantially all of the volatile constituents thereof.

10. A method of making a magnetic material which comprises mixing a finely divided magnetic metal with an insulating composition made up of a water-soluble organic acid, sodium silicate, a ceramic material, and water, heating the resulting mixture to dry it completely,- and simultaneously stirring the mixture to prevent it caking and to cause the insulating composition to coat the particles of magnetic metal.

11. A method of making a magnetic material which comprises mixing a finely di vided magnetic metal with an insulating composition made up of tartaric acid, sodium silicate, a ceramic material, and water, heating the resulting mixture to dry it completely, and simultaneously stirringthe mixture to prevent it caking and to cause the insulating composition to coat the particles of magnetic metal.

12. A method of making a magnetic ma terial which comprises mixing a finely divided magnetic metal with an insulating composition made up of lactic acid, sodium silicate, a ceramic material, and water, heating the resulting mixture to dry it completely, and simultaneously stirring the mixture to prevent it caking and to cause the insulat ing composition to coat the particles of magnetic metal.

13. A method of makin gm magnetic material which comprises mixing a finely divided magnetic metal with an insulating composition made up of citric acid, sodium silicate, a ceramic material, and water, heating the resulting mixture to dry it completely,-and simultaneously stirring the mixture to prevent 'it caking and to cause the insulating composition to coat the particles of magnetic metal.

14. A method of making a magnetic material which comprises mixing a finely divided magnetic metal with an insulating composition comprising a water-soluble organic, acid and abinder, heatin and agitating the resulting mixture to y it comcross RZFE ENOE pletelyin theform of a dust, compressing l' xammer the dust tocause the particles thereof to cohere and form a solid mass, and annealing the mass to relieve internal stresses and to drive ofithe volatile constituents of the mass.

15. A magnetic core part formed of finely divided magnetic metal and an insulating ticles of magnetic metal and including the end-products obtained by heating a mixture of tartaric acid, sodium silicate, and talc, to

a temperature above 400 C.

17. A magnetic core part formed of finely divided magneticmetal and an insulating composition forming a coatin on the particles of magnetic metal and mcludingthe end-products obtained by heating a mixture of lactic acid, sodium silicate, and tale, to a temperature above 400 C.

18. A magnetic core part formed of finely divided magnetic metal and an insulating composition forming a coating on the particles of magnetic metal and including the end-products obtained by heating a mixture of citric acid, sodium silicate, and tale, to a temperature above 400 C.

19. A magnetic core part formed of finely divided magnetic metal and an insulating composition coating the particles of magnetic metal and comprising the productsobtained by heating a mixture of a water-soluble orgame acid, sodium silicate, and. a ceramic binder, to a temperature of about 565 C.

' 20. A magnetic core part formed of finely divided particles of magnetic metal coated with an insulating composition comprising the products obtained by heating a mixture of a water-soluble organic acid, sodium silicate, and a ceramic binder, to an annealing temperature, said particles being held to- 1ggther in fixed relation by an autogenous nd created by compression.

' 21. A magnetic core part formed of finely divided particles of magnetic metal coated with an insulating composition comprising the products obtained by heating a mixture of a water-soluble organic acid, sodium silicate, talc, kaolin, and water, to a temperature sufficiently high to dry the mixture completely, said particles being held together in fixed relation by an autogenous bond created us formed of finely I composition forming a coating on the par- 4 I a 1,eoo,1 aa

silicate, .75 parts of powdered talc, .75 parts of kaolin, and 12 parts of water to each 100 parts of metal, to a temperature subflantially above 100 C.

23. A magnetic core part formed of finely divided magnetic metal and an insulating composition forming a coating on the particles of magnetic metal and consisting of a non-hygroscopic residue of an evaporated mixture of insulating material and a water- .solublegnganic'acid. V 24. magnetic core part formed of finely.

divided magnetic metal and an insulating composition forming a coating on the particles of magnetic metal and consisting of a non-hygroscopic residue of m evaporated mixture of a water-soluble or amc acid,

sodium silicate, and a ceramic binding material.

i In witness whereof, I hereunto subscribe my name. this 20th'day of December, A. D.

CHARLES c, NEIGHBORS. 

